Control system, display device, control-use host computer, and data transmission method

ABSTRACT

A control system including control devices with each control device including a control unit and a display device connected with the control unit via a dedicated communication line and being capable of display corresponding to a control state of the control unit. The display device includes a communication port connected with a control unit and a communication port connected with a data processing device, and a data processing section. Further, the data transmission method includes a dedicated protocol communication transmitting data with a processing device and a common protocol communication transmitting data with another processing device. In addition, the control-host computer used in the control system includes a control unit controlling a control target and a display device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of application Ser. No. 09/674,175,filed Oct. 27, 2000, now U.S. Pat. No. 6,867,749, and PCT/JP99/02204filed Apr. 23, 1999, and claims the benefit of Japanese PatentApplication 10-117117 filed Apr. 27, 1998, Japanese Patent Application10-120343 filed Apr. 30, 1998, Japanese Patent Application 10-148801filed May 29, 1998, Japanese Patent Application 10-232600 filed Aug. 19,1998, and Japanese Patent Application 10-311039 filed Oct. 30, 1998, thedisclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to (i) a control system that has aplurality of control devices each of which includes a method of controle.g., control unit such as a programmable logic controller (hereinafterreferred to as PLC) and a display device displaying a control state ofthe method of control, and that enables transmission between the controlmeans, (ii) a display device for the control system, (iii) a control-usehost computer suitably used in a control system, and (iv) a datatransmission method regarding data transmission between a first dataprocessing device having its own communication protocol specialized foritself like the foregoing control unit and a second data processingdevice having a common communication protocol like apersonal-computer-applied device.

BACKGROUND OF THE INVENTION

In a conventional control system, generally, a PLC is placed at thecenter of control, and a plurality of PLCs and host computers areconnected via predetermined interface circuits directly or indirectlyvia dedicated adapters, so that transmission of control data between thePLCs as well as between the PLCs and the host computers is carried outwith use of communication functions of the PLCs.

However, developed from a sequencer utilizing a relay, a PLC bestperforms in operations related with input/output control, such as anON/OFF control of a switch and an operation of taking in data from asensor, and use of a PLC as a center of data communication will overloadthe PLC, even though such use is possible.

Furthermore, data communication time becomes excessively long, forinstance, upon an initial setting before control when more datatransmission is required, as compared with during control. In a casewhere a personal computer is directly connected to a display device of aPLC to shorten the data communication time, connection change becomesextremely bothersome.

The following description will explain a typical conventional controldevice, while referring to FIG. 24 that is a block diagram schematicallyillustrating an arrangement of the same. A plurality of PLCs (three PLCsin the case of FIG. 24), that is, PLCs 501α, 501β, and 501γ are equippedwith their dedicated display devices 502α, 502β, and 502γ, respectively,and are connected with a host computer 504 via a network circuit 503. Inresponse to a control output of the host computer 504, the PLCs 501α,501β, and 501γ control one or a plurality of apparatuses to becontrolled (not shown), receive states of the control-target apparatusesfrom sensors not shown, and cause the display devices 502α, 502β, and502γ to display the states.

The foregoing PLC 501α, 501β, and 501γ may use different protocols, asindicated with the reference codes of α, β, and γ in FIG. 24, dependingon respective manufacturers thereof, or in some cases, from one PLC toanother PLC even though made of the same manufacturer. Therefore, thehost computer 504 conducts communication with the PLCs 501α, 501β, and501γ via the network circuit 503 according to protocols α, β, and γ,respectively.

Therefore, the display devices 502α, 502β, and 502γ are connected withthe corresponding PLCs 501α, 501β, and 501γ via connection cables 505α,505β, and 505γ, respectively. The display devices 502α, 502β, and 502γsynthesize data expressing control states transmitted according to theforegoing protocols α, β, and γ, respectively, with characters and imagedata installed beforehand, so as to produce display screens and executedisplay. More specifically, for example, changeable data such as dataexpressing the foregoing control states are synthesized with a fixedscreen display in which names of the foregoing apparatuses to becontrolled are added to a background illustrating a manufacturing line,and a resultant screen display is displayed.

Therefore, the foregoing display screen is changed upon a change ofproducts being produced or a producing method, and also it is changedout upon occurrence of an inconvenience.

As described above, the foregoing PLCs 501α, 501β, and 501γ haveoriginally been developed from control-use sequencers using relays, andthey excel in ON/OFF control of switches and functions as input/outputcircuits for taking in data from sensors, whereas they are inferior indata communication functions. Therefore, they are capable oftransmitting data like data expressing control states of the apparatusesto be controlled to the display devices 502α, 502β, and 502γ, but theyare not suitable for transmission of enormous data such as character andimage data.

Therefore, conventionally, upon changes of the display screen, apersonal computer 506 storing the character and image data is taken intothe manufacturing site, and the display devices 502α, 502β, and 502γ setin walls or manufacturing machines are taken out. After the PLCs 501α,501β, and 501γ are turned into a offline state, disconnected to thenetwork circuit 503, the connection cables 505α, 505β, and 505γconnecting the display devices 502α, 502β, and 502γ with the PLCs 501α,501β, and 501γ are disconnected from the display, devices 502α, 502β,and 502γ (indicated by an arrow code φ as to the connection cable 505α).Thereafter, a connection cable 507 extended from the personal computer506 is connected thereto (indicated by an arrow code A as to theconnection cable 507), so that the foregoing character and image dataare installed.

Upon an end of the installation of data, connection of the connectioncables 505α, 505β, and 505γ with the display devices 502α, 502β, and502γ is restored, the display devices 502α, 502β, and 502γ are returnedto their own places in the walls or manufacturing machines, and the PLCs501α, 501β, and 501γ are returned into an online state, with connectionof the same with the network circuit 503 restored.

Therefore, the operation of changing the screen display is complicated,and it is necessary to consecutively connect the personal computer 506with the display device whose screen display is to be changed, one afteranother, for downloading. Therefore, there arises a problem that anoffline time is prolonged.

Furthermore, transmission of a relatively large amount of data upon, forexample, a change of processed products or drastic changes to processingoperation data is also executed by connecting the personal computer 506with the PLCs 501α, 501β, and 501γ and installing preset data such asapplication programs and initial values, like in the foregoing case ofthe foregoing characters and image data.

Furthermore, since the PLCs differ in communication protocols for datacommunication, depending on respective manufacturers thereof, or in somecases from one PLC to another PLC even though produced by the samemanufacturer, there are innumerable communication protocols to which ahost computer has to be suited, and it is necessary to anew preparecommunication protocols that are suited for the PLCs, for dedicated useof the host computer. Thus, there exists a problem of extremeinconvenience.

SUMMARY OF THE INVENTION

The inventors of the present invention examined the foregoing problems,and arrived at the following finding. Namely, having been developed as apersonal-computer-applied device, a programmable display device that hasbeen exclusively used for display is capable of data communication witha generally used personal computer without any problem with use of agenerally used protocol. Furthermore, a display device is necessarilycapable of data communication with a PLC, it is usual that a dedicatedcommunication protocol specialized for a PLC to be connected with thedisplay device has been developed.

Therefore, in the case where this display device is placed at center ofcommunication and each PLC and a host computer are connected to eachother with use of display devices, the display devices function asprotocol converting means in data communication.

Aspects of the present invention have been made based on this finding,and an object of the present invention is to provide a control system inwhich a display device that conventionally was used exclusively fordisplay of a control state is placed at a center of data communication.This ensures that a control unit such as a PLC can be exclusively usedfor I/O control whereby a load on the control unit is decreased. At thesame time, it ensures that innumerable communication protocols ofcontrol units need not be considered on the side of a data processingdevice of the host computer or the like or on the display device side,whereby software operations are reduced.

Furthermore, based on the foregoing finding, an object of the presentinvention is to provide a data transmission method for a system having(i) a first data processing device having its own communication protocolsuch as the foregoing control unit, and (ii) a second data processingdevice having a common communication protocol such as apersonal-computer-applied device, the data transmission method ensuringnormal communication, without causing the second data processing deviceto consider all innumerable specialized communication protocols upondata transmission between the first and second data processing devices,so that software operations for development, management, and maintenanceof the system are reduced.

More specifically, a control system in accordance with an aspect of thepresent invention is a control system including a plurality of controldevices, each control device including a control unit and a displaydevice connected with the control unit via a dedicated communicationline and being capable of display corresponding to a control state ofthe control unit, the control system being capable of transmitting databetween the control devices. The control system includes datatransmitted between the control unit and the display device according toa dedicated protocol specialized for the control unit, and (ii) all ofthe display devices in the control devices are connected with each othervia a common communication line, and data is transmitted between thedisplay devices according to a common protocol.

Incidentally, protocols in a wide sense include protocols (transmissionprotocols) that have to be standardized in a network covering atransmitter and a receiver, for, otherwise data per se cannot betransmitted. Such protocols include: codes indicative of a startcharacter, an end character, etc.; transmitting/receiving timings ofeach character; and methods for identifying the transmitter or thereceiver. The protocols also include command systems that have to bestandardized between the transmitter and the receiver, for, otherwise,an operation requested by one part and an operation executed by theother part do not coincide, thereby making it impossible to normallyexecute operations such as control operations. The aforementioneddedicated and common protocols are realized as combination oftransmission protocols and command systems.

This allows the control unit to be used in exclusively for I/O control,thereby enabling a reduced load on the control unit. Moreover, since thedisplay device should be at least capable of communication according toa dedicated protocol of a control unit connected thereto and accordingto the foregoing common protocol, it is possible to decrease the numberof steps required for production (development) of software.

In addition to the foregoing arrangement, a data processing device maybe connected to the common communication line, and data may betransmitted between the data processing device and each display deviceaccording to the foregoing common protocol.

In the foregoing arrangement, the data processing device is communicablewith any control device as long as the data processing device cancommunicate according to the common protocol. Therefore, in spite of thepresence of the data processing device, time and labor for development,management, and maintenance of the whole control system can be saved.

Furthermore, a display device according to an aspect of the presentinvention includes (i) a first data communication port connected with acontrol unit having a predetermined dedicated communication protocolspecialized for the control unit itself, (ii) a second datacommunication port connected with a certain data processing device,(iii) a data processing section that processes data inputted andoutputted through the first and, second data communication ports, inaccordance with a procedure set beforehand, and (iv) a display sectionthat provides a display corresponding to information processed by thedata processing section, and (a) the display device executes datacommunication with the control unit according to the dedicatedcommunication protocol of the control unit, and (b) the display deviceexecutes data communication with the data processing device according tothe common communication protocol.

By using a display device arranged as above, like in the case of theabove-described control system, a load on the control unit is reduced,while the number of steps required for production (development) ofsoftware is decreased.

Furthermore, in addition to the foregoing arrangement, the displaydevice may be arranged so that the data processing section is alsoconnected with an operating section, so that a timing of data processingand contents of the processing by the data processing section ismanually instructed by means of the operating section. This arrangementallows the display device to be used as operating means of the controlsystem.

Furthermore, a display device arranged as described above may be furtherarranged so as to further include a data input section for downloading,from outside the device, data for communication according to thededicated communication protocol.

The foregoing arrangement ensures communication with the control unit bydownloading programs for communication, data indicative of acommunication format, and other necessary data for a dedicated protocol,without preparing in the display device beforehand all data that allowscommunication according to any one of all dedicated protocols likelyconnected with the display device.

Furthermore, a display device arranged as described above is furtherarranged so as to further include a conversion table storing sectionthat stores a conversion table showing correspondence between specialinformation of the control unit that is extracted from the dedicatedprotocol on one hand and common information transmitted according to thecommon protocol on the other hand, so that the data processing sectionconverts the common information received from the common communicationline, into the special information, referring to the conversion table.

According to the foregoing arrangement, a program for communication isnot prepared for each control unit, but rather a conversion table isprepared for each control unit. Therefore, by only changing theconversion table, communication according to each dedicated protocol isenabled.

Furthermore, in addition to the foregoing arrangement, the displaydevice is further arranged to include a format information storingsection for storing a data transfer format of transfer informationtransmitted according to the dedicated protocol, so that the dataprocessing section produces the transfer information by substituting theconverted special information for an undefined portion of the datatransfer format.

According to the foregoing arrangement, the display device appliesnecessary data to undefined portions of the data transfer format andproduces a command to be transferred with a specific control unit atreal time during an operation of the control system. Therefore,irrespective of where data inputted come from, transmission of data isenabled. Furthermore, even when a control unit to which the data shouldbe transmitted is changed, necessary actions can be taken withoutstopping the system.

Furthermore, a display device arranged as described above is furtherarranged so as to include a protocol determining section that (a) sendsout preset data according to a communication protocol selected fromamong a group of protocols applicable for communication of itself, priorto data transmission with the control unit, and that (b) in the casewhere a response from the control unit coincides with a predeterminedresponse, determines the communication protocol as a communicationprotocol used for the data transmission with the control unit.

According to the foregoing arrangement, the dedicated protocol that thedisplay device uses for data transmission is determined prior toestablishment of data transmission with the control unit. This enablesreduction of time and labor spent by the user, and also prevents errorsin setting, as compared with the case where the user sets the dedicatedprotocol.

On the other hand, a data transmission method in accordance with anaspect of the present invention is a data transmission method appliedwhen a data processing device transmits data with a first dataprocessing device and a second data processing device, the dataprocessing device being provided between the first data processingdevice and the second data processing device, the first data processingdevice transmitting data according to a first communication protocol,and the second data processing device transmitting data according to asecond communication protocol. The method includes (i) a dedicatedprotocol communication operation of transmitting data with the firstdata processing device according to a communication protocol specializedfor the first data processing device, and (ii) a common protocolcommunication operation of transmitting data with the second dataprocessing device according to a communication protocol common to dataprocessing devices that are likely connected with the data processingdevice.

According to the foregoing arrangement, each data processing device iscapable of communication only according to a dedicated protocol of thefirst data processing device connected thereto and according to thecommon protocol. Therefore, as is the case with the foregoing controlsystem, it is possible to decrease the number of operations required forproduction (development) of software.

Furthermore, a data transmission method in accordance with an aspect ofthe present invention is a data transmission method applied when a dataprocessing device transmits data with a first data processing device anda second data processing device, the data processing device beingprovided between the first data processing device and the second dataprocessing device, the first data processing device transmitting dataaccording to a first communication protocol, and the second dataprocessing device transmitting data according to a second communicationprotocol. The method includes (i) a dedicated protocol communicationstep of transmitting data with the first data processing deviceaccording to a communication protocol specialized for the first dataprocessing device, and (ii) a data sending operation of, prior to thededicated protocol communication operation, selecting a communicationprotocol from among a group of protocols possessed by itself and sendingout preset data according to the selected communication protocol, and(iii) a protocol determining operation of waiting for a response fromthe first data processing device, and determining a communicationprotocol to which a predetermined response is obtained as acommunication protocol used for data transmission with the first dataprocessing device.

According to the foregoing arrangement, the data sending operation andthe communication protocol determining operation are performed beforethe dedicated protocol communication operation. This enables reductionof time and labor spent by the user, and also prevents errors insetting, as compared with the case where the user sets the dedicatedprotocol.

On the other hand, a control-use host computer in accordance with anaspect of the present invention is a control-use host computer used in acontrol system that includes (a) a control unit for controlling acontrol target, (b) a display device that communicates with the controlunit via a dedicated network so as to display or control a control stateof the control unit and that, in the case where a common network apartfrom the dedicated network has a communication protocol different fromthat of the dedicated network, converts one of the protocols into theother protocol, and (c) the control-use host computer connected with thedisplay device via the common network. The control-use host computerincludes an interface section that sends data streams containinginstruction contents for the control unit via the common network to thedisplay device connected with the control unit.

According to the foregoing arrangement, the interface section of thecontrol-use host computer gives the display control device informationof instruction contents to the display device via the common network,and the display control device of the control system converts thecommunication protocol so as to transfer the information to the controldevice. Therefore, the interface section of the control systemcommunicates with the common network according to one communicationprotocol irrespective of the communication protocol of the controldevice. Consequently, this allows control devices with differentcommunication protocols to exist together in the control system, andtherefore, saving time and labor in incorporating a control device intothe control system.

Furthermore, since the communication protocol of the interface sectionis uniform irrespective of the communication protocol of the controldevice, there is no need to change the interface section and thetransmission control means of the control-use host computer, even in acase where a new control device is developed. Therefore, as comparedwith the conventional cases where when a new control device isincorporated a program for a communication protocol of the new controldevice is created on both the sides of the display control device andthe control-use host computer, time and labor required uponincorporation of the control device into the control system is saved forthe time and labor required relating to the control-use host computer,and time and labor required for management and maintenance of the wholecontrol system is saved.

Furthermore, in addition to the foregoing arrangement, the control-usehost computer according to an aspect of the present invention isarranged so as to further include a plurality of transmission controlsections that are provided between the interface section and a host-sidedisplay section for controlling or displaying a state of the controltarget and that controls the interface section in response to a requestfrom the host-side display section, so as to transmit or receive datafor controlling or displaying the state of the control target, whereinone of the transmission control sections is a simple transmissioncontrol section that is capable of specifying the request through asimpler procedure than the other transmission control section does.

According to the foregoing arrangement, since at least one of thetransmission control sections is a simple transmission control section,the developer on the host-side control section is allowed to send arequest regarding a degree of difficulty according to his/her ownexpertise, by selecting the simple transmission control section or theother transmission control section. Furthermore, the developer of thetransmission control section is allowed to recommend which transmissioncontrol section should be used, considering expertise of the developerof the host-side display control section. Consequently, it is possibleto prevent errors of the control system caused by a mistake of thedeveloper of the host-side display control section.

Furthermore, a control system in accordance with an aspect of thepresent invention is a control system in which a control device controlsa control target in response to a control output transmitted from a hostdevice, and transmits information about the control to a display deviceso that the information is synthesized and displayed with character andimage data installed beforehand in the display device. The controlsystem includes a display device between the host device and the controlunit, so that the character and image data are downloaded from the hostdevice so as to be installed in the display device.

According to the foregoing arrangement, noting that a display devicedealing with data of a relatively larger amount such as image data has ahigher computing competence and higher applicability to datacommunication as compared with a control unit dealing with data of arelatively smaller amount such as ON/OFF data, this display device isprovided between the host device such as a host computer and the controlunit such as a programmable logic controller, and a control output fromthe host device or control state data from the control unit istransmitted without any trouble via the display device to the controlunit or to the host device, respectively. On the other hand, uponinstalling character and image data that are produced by writing namesof control-target devices on a background screen illustrating, forexample, manufacturing lines, the data is transmitted directly to thedisplay device via a normal communication circuit. Therefore, there isno need to carry out complex operations such as taking the host deviceinto a manufacturing site, changing the wire connection, and the like.Moreover, in the case where a plurality of display devices, that is,control units are connected via a network circuit, character and imagedata can be transmitted to the display devices successively, whereby theinstalling operation can be completed within a short time.

Furthermore, a control system in accordance with an aspect of thepresent invention is a control system in which a plurality of controlunits respectively control targets in response to control outputstransmitted from a host device, and information about the controls isdisplayed in corresponding display devices, respectively. The controlsystem includes a display device between the host device and the controlunit, so that preset data are downloaded from the host device so as tobe installed in the display device.

According to the foregoing arrangement, like in the case where characterand image data are installed, the display devices transfer data to thecontrol units and the host computer, respectively, thereby providingtransmission of data without problems. Furthermore, upon installingpreset data such as application programs and initial values not only tothe display devices but also to the control units, it is possible todirectly transmit the data via normal communication lines. This ensuresa reduction of work upon installation, while also ensuring that theinstalling operation is completed within a short time even in a casewhere a plurality of display devices, that is, control units areconnected.

Furthermore, the control system that enables installation of characterand image data or preset data from the host device is according to anaspect of the present invention arranged so that communication betweenthe control unit and the display device corresponding thereto is carriedout according to a certain protocol, while communication via a networkcircuit between the display device and the host device should be carriedout according to the predetermined common protocol.

According to the foregoing arrangement, taking advantage that eachcontrol unit is connected with the host device via the display devicethat has a high computing competence and high applicability to datacommunication, the display device provides protocol conversion. In sodoing, the control unit is allowed to use an arbitrary protocol thatdiffers depending on the manufacturer or the product, while the networkis made to use the predetermined common protocol, and consequently,extension or change of the control system easily executed.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a structure of a principal partof a control system illustrating an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a structure of a principal partof a control system of another embodiment of the present invention.

FIG. 3 is a block diagram illustrating a structure of a principal partof a control system of still another embodiment of the presentinvention.

FIG. 4 is a block diagram illustrating a network structure of a controlsystem of still another embodiment of the present invention.

FIG. 5 is a block diagram illustrating an example of an arrangement ofhardware of a PLC and a programmable display device in the foregoingcontrol system.

FIG. 6 is a perspective view of an example of an outward, partiallycut-away appearance of the programmable display device.

FIGS. 7A and 7B are explanatory views illustrating an example of controloperations of the foregoing control system.

FIGS. 8A through 8C are explanatory views illustrating an arrangement ofa processing instruction word used in the foregoing control system.

FIG. 9 is a block diagram illustrating a principal part of the foregoingcontrol system.

FIG. 10 is a block diagram illustrating a principal part of a controlsystem in accordance with still another embodiment of the presentinvention.

FIG. 11 is an explanatory view illustrating an example of a datatransfer format used in a common protocol in the foregoing controlsystem.

FIG. 12 is an explanatory view illustrating an example of data transferformat used in a dedicated protocol in the foregoing control system.

FIG. 13 is an explanatory view illustrating an example of a conversiontable used in protocol conversion between a dedicated protocol and acommon protocol in the foregoing control system.

FIG. 14 is a block diagram explaining the foregoing control system inmore detail.

FIG. 15 is a block diagram illustrating a principal part of a controlsystem in accordance with still another embodiment of the presentinvention.

FIGS. 16A through 16B are explanatory views illustrating an example oftables of correspondence between dedicated protocols and response codesin the case where a protocol-identification command is sent out by theforegoing control system.

FIG. 17 is a flowchart illustrating an automatic judging procedure ofthe dedicated protocol in the foregoing control system.

FIG. 18 is a block diagram illustrating a principal part of a controlsystem in accordance with still another embodiment of the presentinvention.

FIG. 19 is a block diagram illustrating a principal part of a controlsystem in accordance with still another embodiment of the presentinvention.

FIG. 20 is an explanatory view illustrating an example of a datatransfer format used in the foregoing control system.

FIG. 21 is a timing chart for explaining a download operation of imagedata from a host side to a display device side in the foregoing controlsystem.

FIG. 22 is a block diagram illustrating a principal part of a controlsystem in accordance with still another embodiment of the presentinvention.

FIGS. 23A through 23G are explanatory views illustrating an example of aformat of data used in the foregoing control system.

FIG. 24 is a block diagram illustrating a principal part of a typicalcontrol system of prior art.

DETAILED DESCRIPTION OF THE INVENTION

The following description will explain the aspects of the presentinvention, referring to examples of the present invention andcomparative examples. Note that however the aspects of the presentinvention are not limited by the examples at all.

[First Aspect]

The following description will explain an aspect of the presentinvention while referring to FIG. 1. As shown in FIG. 1 thatschematically illustrates an overall structure of a control system 1 inaccordance with the aspect of the present invention, the control system1 is provided with a plurality of control devices 5 each of whichincludes a control unit 2α, 2β, a display device 3α, 3β capable ofdisplay suitable to a controlled state of the control unit 2α, 2β and adedicated communication line 4 for connection between the control unit2α, 2β and the display device 3α, 3β so that data can be transferredbetween the control devices 5. In each control device 5, the controlunit 2α, 2β and the display device 3α, 3β execute data communication bymeans of a dedicated protocol inherently specialized for each controlunit 2α, 2β. On the other hand, the display devices of the controldevices 5 are connected with each other via a common communication line6, and execute data communication by means of a common protocol.

In the foregoing arrangement, the display devices 3α, 3β executeprotocol conversion thereby enabling each control device 5 tocommunicate each other by means of a common protocol predetermined.Therefore, even in the case where the dedicated protocols of the controlunits 2α, 2β are different from each other, transfer of data between thecontrol devices 5 is enabled without any difficulties. As a result,control units 2α, 2β using different communication protocols are allowedto exist in one control system, without problems.

Furthermore, the display devices 3α, 3β that have been used exclusivelyfor display of control states are now used as center of datacommunication, and the display devices 3α, 3β execute protocolconversion between a dedicated protocol and a common protocol.Therefore, it becomes possible to use the control units 2α, 2βexclusively for I/O control which is its own function, thereby enablingto reduce a load on the control units 2α, 2β.

Furthermore, if the display device 3α is capable of protocol conversionbetween a dedicated protocol for the control unit 2α connected with thedisplay device 3α and the foregoing common protocol, data transfer isenabled between the foregoing control unit 2α and a control unit 2β viaa display device 3β that corresponds to the control unit 2α,irrespective of the dedicated protocol of the control unit 2β.Therefore, communication protocols specific to the control units 2α, 2βthat are innumerable need not be considered, while only communication bymeans of a dedicated protocol of a control unit that can possibly beconnected thereto, communication by means of the common protocol, andthe protocol conversion between the two may be taken into consideration.Therefore, operations required in production (development) of softwarecan be decreased.

Additionally, even in the case where a control device including acontrol unit 2β that communicates with a new dedicated protocol is addedin the control system 1, there is no need to alter another displaydevice. Therefore, time and labor upon incorporating the control unit inthe control system is saved, whereby time and labor for management andmaintenance of the whole control system is saved.

[Second Aspect]

A control system 20 in accordance with an aspect of the present, asshown in FIG. 2, includes a data processing device 7 connected with acommon communication line 6, to ensure transfer of data between the dataprocessing device 7 and the display devices 3α, 3β using the commonprotocol. This enables various operations such as centralized control bythe host computer, and download of a protocol conversion procedure thatwill be described later.

In this arrangement as well, like in the foregoing control system 1, thedata processing device 7 is capable of transfer of data to and from eachcontrol device 5 by communication using the common protocol alone. As aresult, the data processing device 7 need not produce different sets ofsoftware for dedicated protocols respectively, and therefore, time andlabor necessary for production of software can be reduced. Furthermore,even in the case where a new control device 5 is incorporated in thecontrol system 20, there is no need to alter the data processing device7. Consequently, in spite of the provision of the data processing device7 communicable with a certain control device 5, time and labor fordevelopment, management, and maintenance of the whole control system 20can be saved.

[Third Aspect]

The following description of an aspect of the present invention willexplain in more detail an arrangement of a display device whilereferring to FIG. 3.

Display devices 31α, 31β of a control system 30 in accordance with anaspect of the present invention include a dedicated protocol interfacesection (first data communication port) 11, a common protocol interfacesection (second data communication port) 12, a data processing section13, and a display section 14. The dedicated protocol interface section11 is connected, via a dedicated communication line 4, with a controlunits 2α, 2β in which a dedicated protocol specific to the control units2α, 2β is specified beforehand. The common protocol interface section 12is connected with a certain data processing device such as a dataprocessing device 7 or another display device 31α, 31β, via a commoncommunication line 6 for communication using a predetermined commonprotocol. The data processing section 13 processes datainputted/outputted via the protocol interface sections 11 and 12according to a procedure set beforehand. The display section 14 executesdisplay corresponding to information processed by the data processingsection 13.

Furthermore, for example, the protocol interface sections 11 and 12execute communication using their own communication protocols,respectively, while a data format is converted by the data processingsection 13 as required; consequently, data communication between thededicated protocol interface 11 and the control unit 2α, 2β is executedusing the dedicated protocol, and data communication between the commonprotocol interface section 12 and the data processing device 7 (anotherdisplay device 31α, 31β) is executed using the common protocol.

Furthermore, the data processing section 13 is connected with anoperating section 15 accepting an input from a user, such as a touchpanel or a keyboard, so that instruction of data processing times andprocessing contents of the data processing section 13 can be inputtedmanually via the operating section 15.

Additionally, the display device 31α, 31β in accordance with an aspectof the present invention is equipped with a data input section 16 forinput of data from outside the display device 31α, 31β, such as a memorycard reader, so that data and programs for processing the foregoingdedicated protocols (data for dedicated protocols) can be downloadedfrom outside the display device 31α, 31β. Incidentally, using theforegoing common protocol interface section 12 as the data input section16, the foregoing data or programs may be downloaded from the dataprocessing device 7 or another display device 3β, for example.

The foregoing arrangement enables the display device 31α, 31β to, evenafter being completely fabricated, download data for its dedicatedprotocol when necessary. Therefore, data for dedicated protocols neednot be prepared beforehand as to all the control units 2α, 2β that areconnectable, and consequently, a memory capacity required for thedisplay device 31α, 31β is reduced. Furthermore, even in the case wherea control unit 2 of a new dedicated protocol is developed, the displaydevice has to only download data for the dedicated protocol so as tocommunicate with the foregoing control unit. Furthermore, the data forthe dedicated protocol may be managed by, for example, the dataprocessing device 7 and downloaded as required. Therefore, management ofthe data is also facilitated.

[Fourth Aspect]

The following description of an aspect of the present invention willexplain in more detail an arrangement of the control device, whilereferring to FIGS. 4 through 9. Specifically, as shown in FIG. 4, acontrol system 40 in accordance with an aspect of the present inventionis a system provided with a plurality of PLCs 22α, 22β as control unitsassociated with each other, so that the system is capable of sequencecontrol of a target system 8 such as a belt-conveyer-type automaticassembly system. In the control system 40, a programmable display device32α, 32β is used as a control panel of each PLC 22α, 2β. Furthermore,the control system 40 includes a host computer 71 for centralizedcontrol of the control devices 5 c and for managing data of the controldevices 51α, 51β all together. The programmable display devices 32α, 32βconnected with the forgoing PLCs 22α, 22β constitute a set of a controldevices 51α, 51β. The control system 40 includes two control devices51α, 51β including a first control device 51α and a second controldevice 51α, respectively, or alternatively it may include more than twoof such control devices. In the following explanation, for convenience,Greek characters for distinguishing the sets of the control devices 51α,51β are attached to ends of referential codes like PLC 22α, 22β in thecase where the respective sets are individually referred to.

In the present aspect of the invention, two types of the PLCs are used,PLC 22α and PLC 22β. Each of the PLCs 22α and 22β has its own dedicatedcommunication protocol specialized for the manufacturer and the type ofthe apparatus. PLC 22α and the PLC 22β are capable of executing controlsassociated with each other as will be described later, in a state of,for example, being individually connected with control-target devices 9that are individually provided a belt conveyer.

In the following explanation, for convenience, a case where two PLCs andtwo programmable display device are provided is taken as an example, butaccording to an aspect of the present invention this number can beincreased to three or more, respectively. Furthermore, apart from thePLC, any one of various personal-computer-applied apparatuses may beused as the control unit.

In the PLC 22α, 22β, like a CPU unit or a memory unit, a circuit isformed into a unit for each individual circuit required, and byappropriately adding a unit as required via a bus line, functionsachieved by the PLC 2 c as a whole can be increased/decreased.

The PLC 50 shown in FIG. 5 includes a CPU unit 101 for controlling thePLC 50, an input unit 102 enabling direct input of a detected signalsent from the target system 8 an output unit 103 enabling output of aprocessing operation control signal to the target system 8 a memory unit104 for storing various kinds of data and a computer-linked unit 105enabling predetermined data communication with the programmable displaydevice 3 c. The foregoing CPU unit 101 observes changing states of theinput, output, and computer-linked units 102, 103, and 105. Uponrecognition of changes in data such as input of new data, after applyingnecessary calculating operations thereto the CPU unit 101 makes accessto a corresponding address on the memory unit 104 to rewrite contentsand send data to the output unit 103.

Here, in the memory unit 104, a place for storing state data MD that areinputted/outputted directly to/from the target system 8 or used forcontrol of the target system 8 is provided as to each control-targetdevice 9 to be controlled or displayed, such as a passive member like alevel meter or a limit switch provided on the target system 8, an activemember like a relay or a motor, or a data setting member such as acounter or an inker. Further, a word device is appropriated to data tobe inputted/outputted, in the case where the data are word data such asnumerical values, while a bit device is appropriated for bit data suchas on/off information. Each device has its own device name such as“X000,” and by designating a device name, a place where the data is tobe stored is specified on the memory unit 104. Therefore, only byspecifying and accessing a certain word or bit device in the memory unit104 from inside or outside the PLC 50, a corresponding part of thetarget system 8 can be controlled, or information relating to anoperation state of the corresponding part can be individually taken out.

Incidentally, a PLC has according to an aspect of the present inventionincludes a passive data transmission function, like receiving a commandsent from another data processing device such as the programmabledisplay device, and executes writing/reading of data corresponding tothe command to/from the memory unit 104, or returning a command or datasent thereto without applying changes thereto, but needless to say, asubstantially identical embodiment can be achieved in the case where thePLC has an active data transmission function.

On the other hand, the programmable display device 51 is, along with theforegoing PLC 50, incorporated in an operation table of the targetsystem 8, or alternatively it is independently provided, so as to beused as a control panel for the target system 8.

A programmable display device 51 in accordance with an aspect of thepresent invention is, as shown in FIG. 6 for example, arranged so that adisplay screen 112 of a display 141 as the foregoing display section 14is provided on a front side of a main body case 111 formed in asubstantially rectangular shape, and a touch panel 151 as the foregoingoperating section 15 is provided so as to closely adhere to the displayscreen. On the other hand inside the main body case 111, a displaycontrol circuit 113 shown in FIG. 5 is housed. According to an aspect ofthe present invention, a liquid crystal display panel is used as theforegoing display 141. Furthermore, needless to say, any one of variousmanual operating devices such as a pointing device like a mouse or a keyboard may be used instead of, or in addition to, the touch panel 151.

A basic hardware arrangement of the foregoing display control circuit113 is connected as shown in FIG. 5 via a bus line 114 with a CPU 115and memories, e.g., a ROM 116, and a RAM 117, a touch panel controller118 for controlling the foregoing touch panel 151, and a graphiccontroller 119 for controlling the foregoing display 141. The CPU 115executes a predetermined calculating operation in accordance with asystem program stored in the ROM 116. Results of calculationsappropriately stored in the RAM 117 are developed into bit images on avideo RAM 121 by the graphic controller 119 using various display datastored beforehand in a graphic data storing memory 120 including fontdata for display of characters and still picture data. Then, contentscorresponding to the contents written in the video RAM 121 are displayedon the display screen 112 of the display 141.

Furthermore, the foregoing bus line 114 is connected to a communicationcontroller 511 as the dedicated protocol interface section 11 that isactuated with a dedicated protocol specialized for the circuitarrangement of the PLC, so as to establish communication with thecomputer-linked unit 105 of the foregoing PLC via a dedicatedcommunication line 4 in parallel or in serial.

On the other hand, the foregoing bus line 114 is connected to agenerally used communication adapter 512 such as Ethernet (trademark:Xerox Corp.) as the common protocol interface section 12, so that, forexample, connection with the host computer or another programmabledisplay device is provided via the common communication line 6 composedof communication cables, whereby a local area network (LAN) is formed.In the foregoing LAN, a generally used communication protocol (commonprotocol) such as TCP/IP is used, so as to enable transfer of variouskinds of data between the host computer and each control device, orbetween the control devices.

Furthermore, an example of data transfer between the PLC and theprogrammable display device in the control system in accordance with anaspect of the present invention is as follows: state data storingmemories 17 and 32 that will be described later are provided in theprogrammable display device and the PLC, respectively, and they transferdata with each other so as to possess the same contents. By so doing,the PLC and the programmable display device are allowed to hold statedata of substantially identical contents including the bit device orword device provided on the PLC side, with a minimum time lag.Incidentally, for instance, the state data storing memory 17 is set asone region on the RAM 117 on the programmable display device, while thestate data storing memory 32 is set as one region on the memory unit104.

Here, the programmable display device, as shown in FIG. 7( a), manages ascreen in which one or a plurality of still pictures B or memberpictures J1 is placed on a base screen, as a unit screen. The foregoingstill picture B is a picture such as name plate whose display contentsare not to be changed, while the foregoing member picture J1 is apicture with changes in shape or color or flickering, such as a pictureof a switch. Furthermore, the programmable display device includes aplurality of unit screens for use of data processing, as well as it isarranged so that file numbers F e.g., FL1, FL2 . . . are respectivelyallocated to unit screens, and that a screen displaying requiredoperation contents can be obtained only by switching unit screens bydesignating a file number F.

More specifically, in the foregoing programmable display device, asshown in FIG. 5, an event data storing memory 122 that stores processinginstruction words corresponding to the unit screens, respectively, isconnected with the bus line 114. When one unit screen is selected, aprocessing instruction word W, e.g., WL1, WL2, . . . related to theselected unit screen is read intermittently at extremely shortintervals. Such a processing instruction word W includes a set composedof a file number F, an event name N, and a reference information r, asshown in FIG. 8A: the file number F is indicative of a base screen towhich a display control operation is to be applied the event name Nspecifies an operation content to be executed on the base screen and thereference information r is composed of one or a plurality of pieces ofdata that are referred to as to each event to be executed. Theprogrammable display device executes operations of the contentsidentified by the event names N of the processing instruction word Wsuccessively, while referring to the data in the foregoing state datastoring memory 17 having identical contents of the state data storingmemory 32 of the PLC 70. By so doing, the member picture J1, displaydata, and the like on the base screen are displayed immediately inaccordance with changes to the contents of the bit device or the worddevice of the PLC 70 c.

For instance, the processing instruction word WT that is to enable toinvert the bit device set at a predetermined address position in thestate data storing memory 32 in association of pressing instructionoperations with respect to the touch panel 151 is as follows: as shownin; FIG. 8B, the processing instruction word WT includes a file numberF1 of the base screen, and an event name N1 specifying an operation ofthe touch panel 151 that starts with, for example, “T”, and furtherinclude as the reference information r an input coordinates range X·Ymaking an input operation through the touch panel 151 valid and anaddress A at which data should be rewritten in association with pressingoperations at the touch panel 151.

Furthermore, the processing instruction word WL that is to enable todisplay a predetermined picture at a corresponding position on the basescreen in association with operations at the touch panel 151 is asfollows: as shown in FIG. 8C, the processing instruction word WLincludes a file number F1 of the base screen, and an event name N2specifying display of a member picture J1 that starts with, for example,“L”, and further includes as the reference information r a memberpicture display coordinates range X·Y, a file number FL specifying amember picture to be recalled, and an address A to be referred to upondisplay of a member picture.

Furthermore, as shown in FIG. 7A, upon setting processing instructionwords WL1 and WTI in the event data storing memory 122, the words WL1and WTI are set so that respective coordinates ranges X·Y of the wordsWL1 and WTI coincide with each other, and that the respective referenceaddresses A thereof coincide with each other. Furthermore, a state of“0” of a bit device at the address A in the state data storing memory 17is made to correspond to an OFF state of a switch beforehand, so thatthe PLC 70 executes an OFF operation with respect to the actual switchsetting at the time to be controlled, when the bit device exhibits astate of “0”. Furthermore, in the graphic data storing memory 119, dataindicative of a member picture J1 corresponding to an OFF state of theswitch are stored in association with a reference file number FL1, anddata indicative of a member picture J2 corresponding to an ON statethereof are stored in association with a reference file number FL2.

Here, as shown in FIG. 7A, in the case where a reference address A ofthe state data storing memory 17 is “0”, a programmable display devicereads data indicative of the member picture corresponding to the OFFstate of the switch, from the reference file numbered as FL1 of thegraphic data storing memory 120 based on the processing instruction wordWL1, and develops and displays the read data in the coordinates rangeX·Y on the base screen.

Upon pressing the switch-like member picture J1 on the touch panel, theprogrammable display device searches for a touch-panel-use processinginstruction word WT in the event data storing memory 122, and judges,based on a coordinates instructed by the touch panel, whether or notexists the processing instruction word WT including as coordinatesinformation a range including the foregoing coordinates.

For instance, when a point in the coordinates range X·Y of theprocessing instruction word WT1 is pressed, the programmable displaydevice finds the processing instruction word WTI and inverts the datavalue at the corresponding address A from “0” shown in FIG. 7A to “1”shown in FIG. 7B. Consequently, the PLC 2 c executes a controllingoperation that turns on a switch point corresponding to the address A.Further, since the value of the address A is turned to “1”, the memberpicture J2 illustrating the ON state is read from the reference filenumbered “FL2” in the graphic data storing memory 120 based on theprocessing instruction word WL1, and is displayed in the coordinatesrange X.Y. Thus, the switch-like member picture displayed on the basescreen is also turned from the OFF state (JI) to the ON state (J2).

This arrangement enables display on the display screen 112 by the PLC 70that corresponds to a control state of the target system 8, data inputby fingers through the touch panel, as well as indirect control of thetarget system 8 by the PLC 70.

Here, not only state data MD of the PLC 70 directly connected with theprogrammable display device but also state data of the PLC 2 cindirectly connected thereto via the common communication line 6 can bedesignated as the state data MD that are referred to by the foregoingprocessing instruction word W. For instance, information indicative ofthe PLC 70 or information indicative of the programmable display deviceconnected with the PLC 70 is added in the address A of the referenceinformation r, based on which each control-target device 9 in thecontrol system is may be distinguished. This allows all the PLCs to becontrolled in association with each other, via the programmable displaydevice.

A control system 90 is shown in FIG. 9. Here, as function blocks in thePLC, a dedicated protocol interface section 31, a state data storingmemory 32, and a data processing section 33 are provided. The dedicatedprotocol interface section 31 is realized by the foregoingcomputer-linked unit 105 and the like, for communication using thededicated protocol specific to the PLC. The state data storing memory 32is realized as a region of the foregoing RAM 117, for storing state dataMD including contents of a bit device or a word device set on the PLCside. The data processing section 33 is realized by the CPU 115executing a program stored in the ROM 116 or the like, for processingdata inputted/outputted to/from the target system 8, the dedicatedprotocol interface, etc. Likewise, the host computer 71 includes, ascreen display section 41 for executing screen display, a dataprocessing section 42 for controlling the entirety of the host computer7 c, and a common protocol interface section 43 for communication withthe common protocol.

The foregoing data processing section 42 of the host computer 7 ccarries out a predetermined data processing operation, and displays aresult of the operation on the display screen of the screen displaysection 41. The data processing section 42 sends data to be transmittedto the common communication line 6 via the common protocol interfacesection 43. By so doing the data are transmitted on the commoncommunication line 6 according to the common protocol.

On the other hand, the data processing section 33 of each PLCinputs/outputs signals with respect to the control-target device 9 ofthe target system 8 in accordance with the program set beforehand, aswell as stores data of contents corresponding to a control state at thattime (state data MD) in the state data storing memory 32 set in thememory unit 104. Incidentally, an address in the state data storingmemory 32 at which the data are stored is determined, for example,according to the control-target device 9 and the like. The state data MDchanged are sent according to the dedicated protocol to the programmabledisplay device via the dedicated protocol interface section 31 of thePLC and the dedicated communication line 4, so as to be stored in thestate data storing memory 17. Conversely, when data to change the statedata MD in the PLC are fed via the dedicated communication line 4 fromthe programmable display device, a control operation corresponding tothe changes in the data is carried out with respect to thecontrol-target device 9.

According to an aspect of the present invention, it is arrangedbeforehand that various kinds of data generated in the programmabledisplay device or taken into the programmable display device from thePLC are, automatically at uniform intervals, or appropriately inresponse to a command, fed to the host computer 71, via the commoncommunication line G. This enables a lessening of memory capacityprovided in each programmable display device, and managing of all datatogether by building up a database of data sent from all theprogrammable display devices.

Furthermore, in each programmable display device, necessary data can beretrieved from the host computer at an appropriate timing and displayedon the display screen D of each programmable display device, or utilizedin the control operation of the PLC. Furthermore, it is also informationregarding all the control devices 5 can be obtained by the host computer7 c via any one of the display devices.

Furthermore, according to an aspect of the present invention, to manageall data for communication according to the dedicated protocols(protocol information) together, a protocol database is built up in thehost computer with the protocol information suitable to the PLC thatcould be connected with the programmable display devices.

In the foregoing control systems, at an initial setting of theprogrammable display device, the programmable display device selectsprotocol information corresponding to the PLC connected therewith fromthe protocol database stored in the host computer, and downloads thesame via the common communication line according to the common protocol.This enables mutual data transmission between the programmable displaydevice and the PLC according to the dedicated protocol of the PLC.

Furthermore, the programmable display device is set so that contents ofdata that the programmable display device processes are specified byusing the foregoing processing instruction word W and the processinginstruction word W is stored in the event data storing memory 122, whilethe state data MD of the PLC referred to according to each processinginstruction word W are maintained in the state data storing memory 17.

Upon an end of the initial setting, a normal control operation iscarried out. For instance, in the case where control of a second PLC 22βis conducted using state data of a first PLC 22α, a processinginstruction word is set beforehand as the processing instruction wordset for the second display device 32β and the state data of the firstPLC 22α is referred to and the second PLC 22β executes a controloperation based on the foregoing state data.

In this state, when state data MD is sent to the first programmabledisplay device from the first PLC 22α using the dedicated protocolthereof, the corresponding state data MD is updated in the state datastoring memory 17 of the first programmable display device 3 cα. Thestate data MD thus updated are sent to the state data storing memory inthe second programmable display device 32β using the common protocol inresponse to a reading operation on the second programmable displaydevice 32β side.

Here, in the case where the processing instruction word W is setbeforehand so that the updated state data MD are utilized in a controloperation of the second PLC 22β, the state data MD is furthertransferred to the second PLC 22β, using the dedicated protocol. Thus,the control operations of the second PLC 22β is carried out based on thedata of the first PLC 22α.

Conversely, in the case where state data MD taken in by the secondprogrammable display device 32β is data to be processed by the foregoingprogrammable display device 32β, the data is processed by the secondprogrammable display device without being transferred to the second PLC22β. Then, display corresponding to the state data MD is executed on thedisplay screen of the display.

Furthermore, in the case where data are sent from the host computer tothe first PLC 22α so as to control the control-target device connectedwith the foregoing PLC 22α, data is produced by adding an addressspecifying the first PLC 22α to the data to be transmitted, and is fedto the first programmable display device 32α via the commoncommunication line according to the common protocol.

On the other hand, programmable display device 32α, where data is fedfrom another programmable display device, judges whether the data fedthereto is data to be used by that programmable display device 32α orthe data is to be used by the first PLC 22α. In the case where they arejudged to be the data for the PLC 22α, they are transmitted to the PLC22α according to the dedicated protocol.

Thus, even in the case where the data communication protocols arededicated for the PLCs, respectively, and hence different from eachother, state data MD corresponding to a control state in the PLCs can betransferred via the programmable display device between a plurality ofthe PLCs or between the PLC and the host computer.

According to an aspect of the present invention, the programmabledisplay device has the state data (MD) in itself at all times, that is,the case where the state data storing memories 17 and 32 are provided inthe programmable display device and the PLC, respectively, and theprogrammable display device accesses the PLC side regularly atpredetermined short intervals so that the data contents of the statedata storing memories 17 and 32 should coincide with each other. Asexplained in the descriptions of the embodiments below, however, thestate data may be taken from the PLC side as required, upon occurrenceof a specific event or the like, for example. In the case where thestate data storing memories 17 and 32 are provided on both sides,respectively, however, what has to be done is only designation of theprogrammable display device connected with the PLC and an address in thestate data storing memory 17 in the programmable display device 3 c, andthere is no need to specify a PLC in a format of a counterpart code,etc.

[Fifth Aspect]

The following description will explain in more detail a protocolconverting operation display device, while referring to FIGS. 10 through13. Members having a similar structure (function) as those in theabove-mentioned aspects of the invention are designated by the samereference numerals and their description will be omitted.

A display device 103 includes a protocol converting section 133 and aprotocol information storing section 18, in addition to the protocolinterface sections 11 and 12 and the display section 14. The protocolconverting section 133 executes protocol conversion between a dedicatedprotocol and a common protocol. The protocol information storing section18 stores protocol information that is referred to upon protocolconversion.

Protocol information is divided into (i) a conversion table that showscorrespondence between information specific to the PLCs such as commanddata and information of the common protocol corresponding to thespecific information, and (ii) a format of transfer informationtransferred to/from the PLC (format information), and are stored in aconversion table storing section 181 and a format information storingsection 182, respectively. Incidentally, the storing sections 18 e.g.,181, 182 can be regions on the RAM 117 shown in FIG. 5, for instance.

More specifically, in a dedicated or common protocol used in a controlsystem 101 in accordance with an aspect of the present invention, aformat in which information to be transferred is provided between astart code and an end code as shown in FIG. 11, like a generalasynchronous system data transfer format, is specified as a asynchronoussystem data transfer format C. Data transfer formats specified by PLCmanufacturers, however, differ in not only start codes and end codes,but also contents of data contained in the transferred information andthe order of data provided therein.

Here, a format Cr for data reading and a format Cw for data writing arespecified as data transfer formats to be transferred via the commoncommunication line 6. More specifically, in addition to a counterpartcode for specifying a device to which data are transmitted (forinstance, “A·B . . . ”) and a common code (for instance, “01”) foruniformly specifying a command to be executed (reading command), thedata-reading-use format Cr further includes an address (for instance,“X0001”) at which the reading should be started, and a size of data tobe read, as relevant information attached to the common code.Furthermore, in addition to the counterpart code and the common codethat instructs the data writing, the format Cw specified for datawriting further includes an address at which the writing should bestarted, and data to be written as relevant information. Each of theformats Cr and Cw is expressed as data obtained by providing theincluded data in series with use of ASCII codes of hexadecimal notation.

Between commands having the same contents among commands comprehensibleto each PLC, the foregoing common codes are made uniform, irrespectiveof command codes at the dedicated communication lines 4 (command at eachPLC). Besides, for instance, an order of data of relevant informationsuch as a reading start address and a reading data size in which thedata are transmitted, and expression of data when the data aretransmitted, are also made uniform irrespective of the dedicatedprotocols. This allows the common protocol to uniformly specify acommand to be executed, irrespective of PLCs.

Here, since correspondence between a certain common code and a commandcode (specific code) at the dedicated communication line 4 in one PLCdiffers from that of another PLC, a conversion table in which eachcommon code and a specific code of the PLC currently connectedcorresponding to the foregoing common code are paired is formed, asshown in FIG. 13. Therefore, the display device 103 can convert a commoncode to a specific code or vice versa, referring to the conversion tablecorresponding to the dedicated protocol. Furthermore, for instance, thededicated protocol for protocol conversion can be changed by changing aconversion table used for protocol conversion from a conversion tableTBLα for a dedicated protocol a to a conversion table TBLβ for adedicated protocol β.

On the other hand, as shown in FIG. 12, the foregoing format informationFMT is, among data streams Da transmitted via the dedicatedcommunication line 4, a data stream on a skeleton in which portions thatmay change depending on contents of data to be actually transmitted,such as the contents of data to be read/written per se, a size of thedata, or addresses for reading/writing are undefined, and only purposesof use are defined regarding the undefined portions. Incidentally, ifthe regions for command are undefined, in the case where formatinformation FMT extracted from data streams actually transmitted iscommon among a plurality of commands, the regions for the foregoingcommand may be undefined also, so that format information FMT commonamong these commands can be used.

The foregoing format information and conversion tables are stored in aprotocol data base of the host computer as the aforementioned protocolinformation corresponding to each dedicated protocol, while protocolinformation corresponding to the PLC connected to the display device isread upon initial setting of the display device and is stored via thecommon communication line 6 in the foregoing conversion table storingsection 181 and the format information storing section 182.

In the foregoing arrangement, pieces of protocol informationcorresponding to respective dedicated protocols are individuallyprovided as format information FMT and conversion tables. Therefore, byswitching the protocol information depending on a type of an apparatus,data communication according to a particular dedicated protocol isenabled.

Here, the control system 101 in accordance with the has a data transferformat specified as common communication protocol as described aboveused as often as possible at the reading/writing of data from/to thedisplay device to the PLC, as well as at other occasions (for instance,upon display at the display device, and upon setting of preset data).Consequently, operations except control, such as a displaying operationand an operation of setting preset data, need not be changed for eachdedicated protocol. Therefore, steps in the processes of development,management, and maintenance of software can be decreased.

The following description will explain protocol conversion using theforegoing format information FMT and conversion table while referring toFIG. 14. Incidentally, the control system 141 shown in FIG. 14, unlikethe control system 90 shown in FIG. 9, adopts a method in which thestate data storing memory is provided only in the PLC and the displaydevice reads the state data MD from the state data storing memory 32 inthe PLC upon necessity, as another method for state data transferbetween the PLC and the display device.

For instance, in the case where the second PLC 22β executes a controloperation by utilizing a change in the state data MD in the first PLC22α, the second display device 34α is set to refer to the state data MDof the first PLC 22α in response to a processing instruction word set inthe second display device 34α, and the second PLC 22β is set so as toexecute a control operation based on the state data MD.

In this state, via the common communication line 6, a data readingcommand is launched in the data-reading-use data transfer format Crshown in FIG. 11 to the first PLC 22α, the protocol converting section133 of the first display device 34α refers to the conversion tablestoring section 181, to convert the common code in the transferredinformation to a specific code. Further, the protocol converting section133 refers to the format information storing section 182, to applynecessary data such as a specific code, an address, a size, etc. toundefined portions of the format information FMT, thereby converting thesame into a dedicated format. Thereafter, the data are transferred tothe first PLC 22α via the dedicated communication line 4. Incidentally,as to an address and a size of data transmitted according to thededicated protocol, expression formats (for instance, a bit width), ifdifferent from that of the common protocol, are converted by apredetermined procedure.

The first PLC 22α receiving the data analyzes contents of the data, andretrieves necessary data from the state data storing memory 32.Thereafter, necessary data are sent from the first PLC 22α to the firstdisplay device 34α according to the dedicated communication protocol.

On the other hand, the first display device 34α analyzes contents of thereceived data, referring to the conversion table storing section 181 andthe format information storing section 182. In the case where the dataare judged to be the data last time requested for reading and further inthe case where a processing instruction word W is beforehand set in thedata so as to be used in a control operation of the second PLC 22β, thefirst display device 34α designates the second PLC 22β as thecounterpart code, and sends the same to the second display device 34β byusing the common protocol. Thus, an operation of controlling the secondPLC 22β based on the first PLC 22α is executed.

Incidentally, the data sent to the second display device 34β isprocessed only by the display device 34β, the data is processed in thesecond display device 34β without being transferred to the second PLC22β, and display corresponding to the display screen D of the displaysection 14 is executed.

Furthermore, in the case where data is transferred from the hostcomputer 71 to the first PLC 22α so that the control-target device 9connected to the first PLC 2α should be controlled, the counterpart codeand address for specifying the first PLC 22α are attached to the data tobe transmitted. The resultant data is transmitted to the first displaydevice 34α via the common communication line 6 according to the commoncommunication protocol.

The first display device 34α determines whether the data transmittedthereto is to be used in the display device 34α or to be used by thefirst PLC 22α, referring to the counterpart code. In the case where thedata is to be used by the first PLC 22α, the data is transmitted to thefirst PLC 22α side in a manner identical to that described above, byusing the dedicated communication protocol.

Incidentally, in the above description of the present embodiment, a casewhere a plurality of devices to be subjected to data access are presentand a counterpart code is specified is taken as an example. However, inthe case where the counterpart of data communication is specifiedbeforehand, the counterpart code is unnecessary.

[Sixth Aspect]

Prior to protocol conversion of the foregoing display device, thededicated protocol subjected to conversion has to be selected accordingto a control unit (PLC). This selection of the dedicated protocol may becarried out beforehand by the user of the display device. However, tosave labor and time for setting and to prevent errors in setting, adedicated protocol is preferably selected automatically by the displaydevice. The following description will explain a display device 131capable of automatically selecting a dedicated protocol, while referringto FIGS. 15 through 17. In the following description, for conveniences'sake, a case where dedicated protocols of PLCs that can possibly beconnected with the display device are four kinds, “α, α2, β, and γ” istaken as an example, but the numbers can be appropriately increased ordecreased, needless to say.

More specifically, as shown in FIG. 15, a display device 151 inaccordance with the an aspect of the present invention is provided witha protocol determining data storing section 183 for storing acorrespondence table for dedicated protocol determination use, inaddition to the arrangement of the display device 103 shown in FIG. 10.

The correspondence table is a table in which response codes uponissuance of predetermined protocol-determination-use commands (forinstance, “00”) are listed up with respect to dedicated protocols, asshown in FIG. 16A. Selected as the protocol-determination-use commandsare commands such that response data as different as possible from eachother can be obtained so as to correspond to differences between thecommunication protocols. Here, as shown in the correspondence table ofFIG. 16A, the same response codes are returned like the cases of thededicated protocols α and α2. In this case, another determination-usecommand (for instance, “01”) is set, and a table of correspondencesbetween the dedicated protocols and response data is prepared as shownin FIG. 16B, so that determination of a dedicated protocol should beensured according to a combination of a response code with eachprotocol-determination-use command.

In the foregoing arrangement, actuation of the system at an operation 1(ST1) in the flowchart shown in FIG. 17 is followed by a communicationprotocol determination process that starts at operation 2. In thisprocess, at operation 2, a protocol determination command like “00” isfed from the display device 131 to the PLC 2 c.

At operation 3, in the case where there is no response from the PLC, itis determined that data communication per se with the PLC is notestablished. Then, in the case where it is determined that all theprotocols have been checked at operation 4, it is determined that thePLC is not connected or that its protocol is a protocol other than theprepared ones, and the operation proceeds to operation 5, where thedetermining operation ends. On the other hand, in the case where it isdetermined at the operation 4 that there remains a protocol to bechecked next, a protocol applied at a operation 6 is changed, and theflow returns to the operation 2 so that the aforementioned processingoperation should be repeated. Incidentally, each protocol is selected incorrespondence to the PLC that can possibly be connected with thedisplay device, and it is prepared beforehand in a form like protocolinformation stored in the protocol information storing section 18. Theprotocol information is, for instance, downloaded at the initial settingstage, from a protocol data base stored in the data processing device 7,or the like.

Furthermore, confirmation of a response from the PLC at the operation 3is followed by the proceeding to a step 7 where a correspondence tableregarding to a protocol determination command sent, among thecorrespondence tables stored in the protocol information storing section18, is referred to, and a protocol corresponding to the response code isdetermined. For instance, in the correspondence table shown in FIG. 16A,the communication protocol is determined to be “β” in the case where theresponse code is “20”, while the protocol is determined to be “γ” in thecase where the response code is “30”. Therefore, after the communicationprotocol to be used is confirmed at the operation 8, a normal dataprocessing operation at operation 10 is maintained.

In the case where the response code confirmed at the operation 7 is“10”, the communication protocol can possibly be or “α” or “α2”, andhence cannot be determined. Therefore, this is followed by return to theoperation 1, where the determination command is changed to “01” and anidentical determining operation is carried out. In this case, as shownin FIG. 16B, the protocol is determined to be “α” in the case where theresponse code is “01”, while the protocol is determined to be “α2” inthe case where the response code is “02”. In the case where the responsecode is anything other than those, the communication protocol isdetermined to be something other than those prepared.

Furthermore, in the case where a communication error occurs at operation9 during a normal data processing operation, it is presumed that achanging operation such that the PLC connected to the display device 131is changed to another took place. In such a case, the flow returns tothe communication protocol determining process that starts withoperation 2, in which a communication protocol suitable to the PLC isautomatically set. This enables to complete the communication protocolsetting operation, without an initial setting operation in a state inwhich the display device is suspended.

[Seventh Aspect]

The following description of an aspect of the present invention willexplain an arrangement of a host computer of a control system 187 inmore detail, while referring to FIG. 18. A host computer 87 for controluse includes a common protocol interface section 51 for communicationwith the common network 6, various processing sections 52, and a serversection 53. The processing sections 52 include user processing sections521 through 523 for display or control of the state of the target system8 of the host computer 87, and a setting section 524 for executing thesetting of the whole control system 187. The server section 53 isprovided between the processing section 52 and the common protocolinterface section 51, so as to control the common protocol interfacesection in response to a request from the processing sections or thelike. Furthermore, in the server section 53, in addition to a dataprocessing section 55 that controls the common protocol interfacesection 51 so as to cyclically store data from each PLC to a storingsection 54, there are provided a DDE server section 56, a functionprocessing section 57, and a function simple-processing section 58, sothat the data processing section 55 and the various processing section52 communicate each other through a plurality of procedures.

The foregoing DDE server section 56 functions as a server for dynamicdata exchange (DDE) defined by an operating system. Therefore, in thecase where the processing section 52 is a user processing section 521capable of operating as a DDE client, the user processing section 521and the DDE server section 56 can transmit data mutually withouttroubles.

Thus, since the server section 53 in accordance with an aspect of theinvention is provided with the DDE server 56, the processing sections 52previously described are applicable for the foregoing purpose as long asthe processing sections 52 are capable of functioning as clients in DDE.Incidentally, in the case where the control system 187 has been usedsince before, the processing sections 52 are specialized for eachcontrol system 187, and it is often bothersome to produce new processingsections 52. Besides, the processing sections 52 are often arranged soas to transmit data through a procedure defined by the operating systemof the host computer 87, such as DDE, so as to be associated withanother application that operates on the operating system of the hostcomputer 87. Therefore, in many cases, the processing sections 52 can beapplied without troubles.

Furthermore, since the foregoing DDE is defined by the operating system,relatively many applications that are available in the market canoperate as DDE clients. Therefore, even in the case where the processingsections 52 are not used, a user processing section 521 can berelatively easily prepared by using these applications.

Furthermore, as described above, each display device 318, including dataprocessing section and the host computer 87 communicate mutuallyaccording to the common protocol, irrespective of a type of the PLCconnected with the display device 318. Therefore, when the PLC connectedwith the display device is changed or when a newly developed PLC isconnected thereto, the foregoing DDE server section 56 need not changeits operation. Consequently, time and labor for developing programs ofthe host computer 87 can be drastically saved as compared with the casewhere different DDE server sections 56 are prepared for each PLC asconventionally, and therefore, time and labor can be saved uponincorporation of a new PLC to the control system 187.

Incidentally, the foregoing DDE is a procedure defined by the operatingsystem for dynamic data exchange between various applications, and isnot necessarily optimized for control of the control-target devices 9.In result, in the case where the data exchange with the processingsections 52 is limited to DDE, the processing rate can possiblydecrease, and some processing operations cannot be executed.Consequently, the server section 53 in accordance with the presentembodiment is provided with the function processing section 57 and thefunction simple-processing section 58, for exchange of data with theprocessing sections 52 by a procedure other than DDE.

The foregoing function processing sections 57 and 58 are interfacesbetween the foregoing data processing section 55 and the processingsections 52 that require a processing operation that cannot be executedor whose processing rate is insufficient in the case of data exchange byDDE, such as the user processing section 522 or 523 that executeshigher-level processing operations as compared with the user processingsection 521, or the setting section 524 that executes the setting of thewhole control system 187. For instance, the function processing sections57 and 58 can be realized as DLL (dynamic link library) in Windows asthe operating system of Microsoft Co. Among the function processingsections 57 and 58, the function processing section 57 includes asrecallable functions all the functions that the data processing section55 can possibly be requested to do by the processing sections 52, suchas all the settings conducted by the setting section 524, display andcontrol of data from the control-target devices 9, the PLCs, and thedisplay devices 318, etc. Incidentally, the foregoing settings includethe setting upon incorporation of a display device 318 into the commonnetwork 6, the setting of each PLC connected with each display device318, and the setting of relationship between the control-target devices9 and device addresses. Thus, the processing sections 52 can control allthe functions of the data processing section 55 by recalling eachfunction of the function processing section 57.

For instance, in the case of a function for reading data from acontrol-target device 9, an IP address of a display device 318, a nameof the control-target device 9, etc. are given as arguments, whilesuccess/failure of the reading, data read out, etc. are returned asreturned values, like in the DDE case. The function is optimized fordata reading from the control-target device 9, unlike the DDE case.Therefore, an amount of data transmitted from the processing sections 52to the data processing section 55 or processed therein upon reading ofdata can be decreased. Furthermore, the link setting is unnecessary.Therefore, in the case of an identical processing operation, theprocessing rate can be improved, as compared with the DDE case.Furthermore, in the case where an optimal procedure is different evenwith respect to a similar processing operation, functions are preparedfor respective processing operations so that the processing operationscan be carried out through the optimal procedures, respectively.Therefore, by selecting and using an optimal function for eachprocessing operation, the processing rate can be improved as comparedwith the later-described case where the function simple-processingsection 78 is utilized. Furthermore, processing operations such assettings of various kinds and transmission of data at specified timings,which cannot be defined by DDE, can be realized.

On the other hand, in the function simple-processing section 58, thereare provided, among the functions prepared by the function processingsection 57, only functions that can be used relatively easily and thatcannot be executed at a sufficient speed by DDE. Functions satisfyingthe foregoing requirements include a function for reading data from aPLC via a display device 318, and a function for writing data from a PLCvia a display device 318. These functions do not provide return valuesbefore the writing and reading operations are completed, whereby controlis not returned to the processing sections 52. Incidentally, in thepresent embodiment, the functions are realized by recall of functions inthe function processing section 57 by the function simple-processingsection 58, but the function simple-processing section 58 may controlthe data processing section 55 directly.

Thus, as to the function simple-processing section 58, the number offunctions prepared, the number of arguments, and the timings for returnof control to the processing sections 52 as recalled are furtherlimited, as compared with the case of the function processing section57. Therefore, use of only the functions of the functionsimple-processing section 58 in producing the user processing section522 enables to save time and labor for selecting optimal functions fromamong similar functions, time and labor for conducting the setting ofarguments and the initial setting in order to use optimal functions, andtime and labor for considering timings of control. Consequently, thoughthe processing rate is higher than in the DDE case, the user processingsection 522 can be created relatively easily.

Here, since the host computer 187 communicates according to the commonprotocol, the foregoing function processing section 57 or the functionsimple-processing section 58 need not change its operation, even in thecase where the PLC connected to the display device is changed or in thecase where a newly developed PLC is connected thereto. Consequently,time and labor for developing a program of the host computer 87 can bedrastically saved, as compared with the case where different functionprocessing sections 57 and different function simple-processing sections58 are prepared for each PLC. Therefore, time and labor required uponincorporation of a new PLC in the control system 187 can be saved.

Additionally, the server section 53 in accordance with the presentaspect is equipped with the two function processing sections 57 and 58whose degrees of difficulty in recalling differ from each other.Therefore, the developer of the server section 53 is allowed torecommend use of the function processing section 57 or use of thefunction simple-processing section 58 depending on respective expertiseof the developers of the processing sections 52 and respective necessaryfunctions of the processing sections 52. Consequently, errors of thecontrol system 187 caused by a mistake of the developers of theprocessing sections 52 can be prevented more surely, as compared withthe case where only the function processing section 57 is provided, inspite of that more complex or higher-speed processing is possible ascompared with the case where only the function simple-processing section58 is provided. Incidentally, the present embodiment is explained bytaking as an example the case where there are two different degrees ofdifficulty of the function processing sections, but a plurality offunction processing sections with different degrees of difficulty may beprovided so that the same effect can be achieved.

Furthermore, in the foregoing embodiment, there is provided the DDEserver section 56 that is capable of recalling data through a simplerprocedure than those of the function processing sections 57 and 58, anddata can be exchanged to some extent without development of theprocessing sections 52. Therefore, errors upon development of theprocessing sections 52 can be further reduced, whereby errors inoperations of the control system 187 can be prevented.

[Eighth Aspect]

Incidentally, the foregoing first through seventh aspects of the presentinvention are described by taking as an example the case where datatransmitted through the common communication line 6 are mainly data forcontrol of the control unit 2, but identical effects such as reductionof time and labor in development, management, and maintenance of thecontrol system 1 can be achieved in the case where other data such asimage data like background images, initial values, or applicationprograms are transmitted.

The following description will explain, as an embodiment of the presentinvention, the case where characters and image data to be used ininformation display concerning PLC control are transmitted, whilereferring to FIGS. 19 through 21.

FIG. 19 is a block diagram schematically illustrating a control system191 in accordance with an aspect of the present invention. PLCs 2 cα, 2cβ, and 2 cγ control control-target devices 91 such as a motor and anelectro-magnetic valve, among control-target devices 9, in response to acontrol output of a host computer 197. Further, the PLCs 2 cα, 2 cβ, and2 cγ detect controlled states of the foregoing control-target devices91, by means of sensors 199 among the control-target devices 9, andtransmit the detected results to the host computer 197, so that theresults are used in display and calculation, and further, analysis, ofthe foregoing control output, as well as they are subjected to imagedisplay by means of corresponding display devices 3 gα, 3 gβ, and 3 gγ.Thus, the foregoing control device controls manufacturing devices,manufacturing lines, etc.

Incidentally, in the example shown in FIG. 19, three PLCs with referencecodes 2 cα, 2 cβ, and 2 cγ are provided, but needless to say, one, ortwo, more PLCs may be provided, and a plurality of the host computers197 may be provided. In the example shown in FIG. 19, control-targetdevices 91 and sensors 199 corresponding to the PLCs 2 cβ and 2 cγ areomitted for simplification of the drawing.

The PLCs 22α, 22β, and 22γ are connected to the display devices 193α,193β, and 193γ corresponding thereto with use of connection cables 194α,194β, and 194γ as the foregoing dedicated communication lines,respectively, so that data transmission should be carried out accordingto dedicated protocols α, β, and γ, that are predetermined according tomanufacturers and versions of the PLCs 22α, 22β, and 22γ.

What should be noted is that the display devices 193α, 193β, and 193γ inaccordance with the present aspect are provided between the PLCs 22α,22β, and 22γ and the host computer 197, respectively, unlike in theconventional cases. The display devices 193α, 193β, and 193γ have beendeveloped as personal-computer-applied devices that are thereforecapable of easily executing communication with general-use personalcomputers according to a general-use protocol δ. On the other hand, thededicated protocols α, β, and γ have been developed with respect to thecorresponding to the PLCs 22α, 22β, and 22γ, respectively, to which thedisplay devices are necessarily connected.

Therefore, the display devices 193α, 193β, and 193γ that are connectedwith the host computer 197 via the common communication line 6 realizedby a network circuit such as an Ethernet (registered trademark), and acommon protocol, such as a protocol for the TCP/IP, is used as theprotocol for the above communication. Thus, protocol conversion betweenthe protocol δ and the protocols α, β, and γ is performed by the displaydevices 193α, 193β, and 193γ, respectively.

The common communication line 6 is connectable, for maintenance or thelike, with an external host 10 provided at a distance, for example, atmanufacturers of the display devices 193α, 193β, and 193γ, respectively,via routers or public telephone lines.

In the host computer 197, a network file 62 composed of node informationconcerning which node is connected with what type of a display device,symbol names of control-target devices and sensors connected with thePLCs 22α, 22β, and 22γ, is formed beforehand by a setting section 61,and respective control outputs to the PLCs 22α, 22β, and 22γ aretransmitted to the common communication line 6 via a common protocolinterface section 64 from an application section 63, with reference tothe network file 62. The control outputs are transmitted to the PLCs22α, 22β, and 22γ via the display devices 193α, 193β, and 193γ,respectively, so as to cause the control-target apparatus 9 a to besubjected to control in response to the control outputs. Further, when acontrol state such as a detection result of the sensor 199 is sent outfrom each display device, the data are returned to the applicationsection 63 via the common protocol interface section 64, so as to beused in the display, calculation and analysis of control outputs.

Furthermore, in the host computer 197, image data of images displayed ondisplay screens of the display devices 193α, 193β, and 193γ, conversiondata for conversion between the protocols α, β, and γ and the commonprotocol δ, etc. are registered beforehand in a data file 65. The imagedata are fed to a display device necessitating the same via the commonprotocol interface section 64, upon maintenance such as a change to aproduct to be processed or an order of processing. The conversion datais fed to a display device necessitating the same via the commonprotocol interface section 64, upon maintenance such as a change to aPLC to be connected with the common communication line 6.

In response to this, each display device 193α, 193β, and 193γ has adedicated protocol interface section 11 connected with the PLC, a commonprotocol interface section 12 connected with the host computer 197, aprotocol conversion circuit 139 for mutual conversion of the protocols,a display panel 194 as the display section, an input section 15, and animage memory 19. Command data is attached to the foregoing controloutput or image data as will be described later, so that the commonprotocol interface section 12 along with the protocol conversion section139 executes protocol conversion in the case where the command data area control output, or writes the data into the image memory 19 in thecase where the data are image data. Upon completion of updating of theimage memory 19, displayed contents on the display panel 194 areupdated. The image memory 19 stores, for example, invariable charactersand image data such as a background screen illustrating manufacturinglines with names of control-target devices and units attached thereto.Variable data representing a control state inputted from the protocolconversion circuit 139 are synthesized with the foregoing character andimage data, and an image of the same is displayed by the display panel194.

The display devices 193α, 193β, and 193γ are integrally incorporatedalong with the corresponding PLCs 22α, 22β, and 22γ in an operation deskof manufacturing lines or the like, or are independently provided, so asto be used as a control panel or the like. On a front side of thedisplay panel 194, an input section 15 such as a touch panel isprovided, and data input, indirect control of a control-target device91, etc. can be executed in response to an inputted result. The displaydevices 193α, 193β, and 193γ are arranged substantially identical to agenerally-used personal computer as described above, and in each, acentral processing unit, memories like ROM and RAM, an external memorydevice such as a hard disk device, a graphic controller, and acommunication controller are connected mutually.

FIG. 20 is a view of an example of a data format, illustrating a dataformat Dδ according to the common protocol δ on the common communicationline 6, and data formats Dα through Dγ according to the protocolsdedicated for the PLCs 22α to 22γ, respectively. The figure exemplifiesa case where the foregoing common communication line 6 is an Ethernet.

More specifically, the protocol δ on the common communication line 6side is arranged so that normal main data following to header data D1and D2 are divided into command data D31 and main data D32. The commanddata D31 represent a command such as writing or reading, and at the sametime, in the present embodiment, they also indicate whether it is normaldata communication between the PLCs 22α, 22β, and 22γ and the hostcomputer, or it is a downloading operation of image data from the hostcomputer to the image memories 19 in the display devices 193α, 193β, and193γ.

Each of the protocols α, β, and γ on the PLCs 22α, 22β, and 22γ sides iscomposed of, following to a header d1, command data d2, address data d3,main data d4, and end data d5. The main data D32 are composed of addressdata d3 of the foregoing control-target devices 91 and sensors 199,etc., and main data d4 representing numerical values and ON/OFFinformation.

The common protocol interface section 12 and the protocol conversionsection 139 constitute a 2-way driver that executes communication withthe host computer 197 as well as communication with the PLCs 22α, 22β,and 22γ, and conducts protocol conversion of data inputted/outputted byusing protocol conversion data supplied from the foregoing data file 65at real time.

Such protocol conversion can be conducted by using conversion tables forconversion between the foregoing protocol δ common on the commoncommunication line 6 and the respective protocols α, β, and γ dedicatedfor the PLCs 22α, 22β, and 22γ, conversion functions, etc., and suchtables or functions are stored beforehand in the aforementioned datafile 25, so as to be selected upon creation of the network file 62 forthe setting of types of the display devices 193α, 193β, and 193γ thatare respectively connected with the aforementioned nodes, and to be setin the protocol conversion section 139.

FIG. 21 is a timing chart for explaining downloading operation of imagedata from the host computer 197 or the external host 10 to the imagememories 19 of the display devices 193α, 193β, and 193γ. At operations1, the host side conducts a node search for searching which node isconnected with what type of a display device, and at operation s2 thedisplay devices 193α, 193β, and 193γ successively respond thereto, alongwith status information including indication of the nodes connectedtherewith, as well as their types.

At operation s3, image-data-transmission start data are fed from thehost side, and at operation s4, acknowledge is returned from the displayside. Then, at operation s5, actual transmission of image data isstarted. Upon completion of transmission of one packet of image data atoperation s5, acknowledge is returned from the display side as shown ata step s6 in the figure. Then, upon completion of downloading of apredetermined amount of display data, that is, an entirety or a part ofthe image data of one display screen, image-data-transmission end dataare supplied from the host side as shown by operation s7. Then, uponreturn of acknowledge from the display side at operation s8,transmission of image data ends.

As described above, in the present embodiment, unlike in conventionalcases, display devices 193α, 193β, and 193γ that excel in computationand that have high applicability to data communication are providedbetween the PLCs 22α, 22β, and 22γ and the host computer 197 or theexternal host 10. Therefore, it is possible to transmit control outputsfrom the host computer 197, control state data from the PLCs 22α, 22β,and 22γ, etc. without difficulties via the display devices to the PLCs22α, 22β, and 22γ and the host computer 197. On the other hand, since itis possible to download image data directly to the image memory 19 viathe common communication line 6 from the host computer 197 or theexternal host 10, there is no need to carry out complex operations eachtime a product or a producing method is changed, such as an operation oftaking a personal computer or the like for the downloading use into amanufacturing site, changing the wire connection, and downloading thedata. Thus, it is possible to extremely improve the workability.

Furthermore, there is no need to temporarily stop the functions of thedisplay devices 193α, 193β, and 193γ upon downloading, for example, toonce turn the display devices 193α, 193β, and 193γ into offline states,then download data, and thereafter again turn them into online states.Moreover, since it is possible to successively download data to thedisplay devices 193α, 193β, and 193γ without changing the wireconnection as described above, a time while the line is stopped can beextremely decreased.

Furthermore, since protocol conversion between the dedicated protocolsα, β, and γ and the common protocol δ is performed by the displaydevices 193α, 193β, and 193γ, respective programs with differentprotocols dedicated for the PLCs 22α, 22β, and 22γ need not be providedon the host computer 197 side, and a program can be produced with thecommon protocol δ. Thus, steps for producing a program can bedrastically simplified.

[Ninth Aspect]

The following description of an embodiment of the present invention willexplain another example of data transmitted through the commoncommunication line 6, referring to FIGS. 22 and 23A through 23G. In theexample, preset data that are set beforehand in the control unit 2and/or the display devices 3, like initial values or applicationprograms, are transmitted.

FIG. 22 is a block diagram illustrating a functional arrangement of acontrol device in accordance with another aspect of the presentinvention that is similar to the arrangement shown in FIG. 19 describedabove, in which the members having a similar structure (function) asthose in the above-mentioned aspects will be designated by the samereference numerals and their description will be omitted. In the presentaspect, a memory 20 is provided in each of the display devices 322α,322β, and 322γ. In the memory 20, like the image memory 19, data isinstalled by downloading the same from the host computer 227. The datathus installed are preset data such as application programs or initialvalues, for example, and may be preset data for the display devices322α, 322β, and 322γ, or may be preset data for the PLCs 22α, 22β, and22γ.

In the case where preset data is downloaded, preset data is transmittedaccording to the common protocol δvia the common communication line 6from the host computer 7 g, and the common protocol interface section 12determines based on the aforementioned command data that the data arepreset data to be installed, and causes the data to be stored in thememory 20. In the case where the preset data thus stored is data for thePLCs 22α, 22β, and 22γ, the display devices 322α, 322β, and 322γ outputcommands for stop of operations to the PLCs 22α, 22β, and 22γ, andthereafter, the preset data thus stored are successively subjected toprotocol conversion by the common protocol interface section 12 and theprotocol conversion section 13 h, and are transmitted to the PLCs 22α,22β, and 22γ. Upon completion of the transmission, a command forresumption of operations is outputted thereto.

FIGS. 23A through 23G are views illustrating an example of a data formatof data to be downloaded to the display devices 322α, 322β, and 322γ.FIG. 23A illustrates the main data D32 in FIG. 20, which in the presentembodiment are further divided into a header D321 and data D322. Theheader D321 is composed of type data D3211 and number data D3212. Theforegoing type data D3211 represent a rough classification regardingwhich type of data the data D322 following thereto are, the foregoingimage data, the system setting data, or other data. The number dataD3212 represent a specific classification regarding where the data D322following thereto are ranked, among the foregoing types of data.

For example, in FIG. 23C, “B” as the type data D3211 indicates that dataare image data, and “000” as the number data D3212 indicates that thedata are image data upon processing a product A. In FIG. 23D, the dataare also image data, and “001” as the number data D3212 indicates thatthe data are image data upon processing a product B.

In FIG. 23E, “S” as the type data D3211 indicates that the data aresystem setting data for the display devices 322α, 322β, and 322γ, and“100” as the number data D3212 indicates that the data are data forconversion between the dedicated protocols α, β, and γ and the commonprotocol δ. In FIG. 23F, the data are also system setting data, and“201” as the number data D3212 indicates that the data are a dataproviding time table that specifies timings of data transmission fromthe display devices 322α, 322β, and 322γ to the host computer 7 g. InFIG. 23G, the data is also system setting data, and “202” as the numberdata D3212 indicates that the data is a status format such as a bitlength, presence/absence of codes, etc. upon data transmission from thedisplay devices 322α, 322β, and 322γ to the host computer 227.

Incidentally, such classification as above of data is performed alongwith the classification according to the foregoing command data D31, oralternatively, either of them may be performed.

The foregoing operation for downloading preset data can be carried outin a manner similar to that shown in FIG. 21, by transmittingpreset-data-transmission start data at the operation s3 and transmittingpreset-data transmission end data at the step s7 from the host side inFIG. 21.

Thus, not only the foregoing image data, but also a relatively largeamount of preset data produced on the host computer 227 side with use ofvarious application programs upon a change of a product produced or adrastic change in processing data can be downloaded to the displaydevices 322α, 322β, and 322γ and/or the PLCs 22α, 22β, and 22γ. In thedownloading of data to the PLCs 22α, 22β, and 22γ particularly, complexworks such as connection of a personal computer become unnecessary, andthe workability can be extremely improved, while a time while a line isstopped can be shortened.

Furthermore, since the preset data for each of the PLCs 22α, 22β, and22γ can be produced according to the common protocol δ, steps requiredfor producing data can be remarkably simplified. Furthermore, in thecase where many PLCs are connected to the common communication line 6 inlarge-scale manufacturing lines or the like, traffic increases and loadson communication also increase. Therefore, if the PLCs are directlyconnected to the network circuit 503 as conventionally, the foregoingdownloading operation is difficult to be carried out. Conversely, it canbe carried out without troubles by providing display devices with highdata communication applicability as in the present invention.

Incidentally, in the foregoing descriptions, the case where protocolinformation is downloaded from the host computer e.g., 71, 227, dataprocessing device 7 is explained, but instead of, or in addition to, thedownloading of protocol information from the host computer,reading/writing of data with respect to a memory card may be provided sothat information may be downloaded from the memory card, or informationmay be downloaded from a loader at appropriate timings such asproduction of a display screen, or alternatively, a plurality of kindsof communication protocols may be prepared in a ROM beforehand so that anecessary communication protocol may be selected. However, since newdedicated protocols are often developed, a display device is provided sothat protocol in information is downloaded thereto from outside.Incidentally, in the case where a protocol dedicated for a control unitconnected to a display device is invariable, it may be fixed in a ROMbeforehand.

Furthermore, in the foregoing embodiment, the display devices and thehost computer are connected mutually via the generally usedcommunication protocol, but alternatively a dedicated communicationprotocol that is common to all the display devices but is specializedonly for these display devices is applicable. Furthermore, each displaydevice may be equipped with data input/output means like a video camerain addition to a PLC, so that various kinds of data such as video datacan be transmitted via the display devices and the common communicationline.

Furthermore, it is possible to arrange that a plurality of PLCs areconnectable with the dedicated communication line and data transmissionis carried out with one display device involved. Furthermore, shown asan example is a case where a type of a PLC to access is specified andreading/writing of data is carried out with a specific addressdesignated for the PLC, but alternatively the following arrangement maybe taken: as to address also, address display common for all the PLCs isset beforehand, and address display expressed in a manner dedicated foreach PLC and a conversion table is prepared. In the latter case, it ispossible to make a program without a type of PLC to access taken intoconsideration, whereby the applicability of the program is improved.

Incidentally, in the foregoing aspects, a control system including adisplay device and a control unit is taken as an example in explanation,but the present invention is not limited to this arrangement. Aspects ofthe present invention are widely applicable to a system including firstdata processing means e.g. control unit having its own dedicatedcommunication protocol, second data processing means e.g., displaydevice, data processing device having a common communication protocolsuch as a personal-computer-applied device, and data processing meanse.g. display device provided between the foregoing two, making mutualtransfer of data possible.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

INDUSTRIAL APPLICABILITY

As described above, in a control system in accordance with the presentinvention, a display device, is applied as center of data communication.This allows a control unit that had conventionally been also used indata communication now to be used exclusively for control, that is, I/Ocontrol, thereby reducing loads on the control unit. Furthermore, thedisplay device side or the host computer side connected with the displaydevice need not consider innumerable communication, protocols of thecontrol units. This ensures a decrease in the number of operationssoftware necessary for development, management, and maintenance of acontrol system.

Furthermore, according to a data transmission method in accordance withan aspect of the present invention, data is transmitted to a first dataprocessing device like a PLC according to a communication protocol(dedicated protocol) dependent on the first data processing device asconventionally, while data is transmitted to a second data processingdevice other than the foregoing devices according to a commoncommunication protocol that is common to all the second data processingdevices. Furthermore, a communication code (program) dedicated for eachdevice is not provided, but rather a conversion table is provided foreach device, so that data to be transmitted to the first data processingdevice are produced at real time by using the conversion table during anoperation of the system. This ensures a decrease in the number of stepsof software like the foregoing control system, while it also ensuresimmediate response to a change of the first data processing devicewithout stopping the system.

Furthermore, a dedicated protocol is determined in the following manner:before data transmission with the first data processing device accordingto a dedicated protocol, predetermined data is sent and the dedicatedprotocol is determined based on a response to the foregoingpredetermined data from the first data processing device. This ensuresreduction of time and labor in setting, as compared with the case wherethe user determines the dedicated protocol, thereby enabling preventionof errors in the setting.

1. A data transmission method, applied when data is transmitted betweena display device and a control unit and between said display device anda data processing device, said display device being provided betweensaid control unit and said data processing device, said control unittransmitting data according to a dedicated protocol, and said dataprocessing device transmitting data according to a common protocol, saidmethod comprising: dedicated protocol communicating includingtransmitting data between said display device and said control unitaccording to the dedicated protocol; and common protocol communicatingincluding transmitting data between said data processing device and saiddisplay device according to the common protocol, wherein in said commonprotocol communicating, communication is conducted between said displaydevice and said data processing device via a common communication line.2. A storage medium storing a program that causes a computer to functionas a display device provided between a control unit and a dataprocessing device so as to transmit data to said control unit accordingto a dedicated protocol and transmit data to said data processing deviceaccording to a common protocol, said storage medium storing said programthat causes said computer to execute: dedicated protocol communicatingincluding transmitting data to said control unit according to acommunication protocol specialized for said control unit; commonprotocol communicating including transmitting data to said dataprocessing device according to a communication protocol common to thedata processing device that is connected with said display device; andcommunication protocol converting including converting the commonprotocol into the dedicated protocol; and as a program for execution ofsaid communication protocol conversion, said program that causes thesaid computer to execute sub-steps of: holding special information ofsaid control unit extracted from the dedicated protocol and informationthat is common among said common protocols corresponding to the specialinformation, in a form of a conversion table; and converting commoninformation sent from said data processing device into specialinformation of said control unit, referring to said conversion table. 3.A storage medium storing a program that causes a computer to function asa display device provided between a control unit and a data processingdevice so as to transmit data to said control unit according to adedicated protocol and transmit to said data processing device accordingto a common protocol, said storage medium storing said program thatcauses said computer to execute: dedicated protocol communicatingincluding transmitting data with said control unit according to acommunication protocol specialized for said control unit; data sendingincluding, prior to said dedicated protocol communicating, sending aprotocol determination command from said display device to said controlunit, the protocol determination command being used for selecting, fromamong a group of protocols, a communication protocol to be used for datatransmission between said control unit and said display device possessedby itself and sending out preset data according to the selectedcommunication protocol; and protocol determining including waiting for aresponse from said control unit, and determining a communicationprotocol to which a predetermined response is obtained, as acommunication protocol to be used for the data transmission between saidcontrol unit and said display device.
 4. A data transmission method asset forth in claim 1, further comprising: communication protocolconverting including converting the common protocol into the dedicatedprotocol, the communication protocol converting comprising: holdingspecial information of said control unit extracted from the dedicatedprotocol and information that is common among the common protocolscorresponding to the special information, in a form of a conversiontable; and converting common information sent from said data processingdevice into special information of said control unit, referring to saidconversion table.
 5. The data transmission method as set forth in claim4, said communication protocol converting comprising: holdinginformation about a data transfer format of transfer informationtransmitted between said control unit and said display device,converting command data using the common information supplied from saiddata processing device, into the special information corresponding tothe command data, by using said conversion table, and converting theconverted special information into transfer information specialized forsaid control unit, by substituting the converted special information forundefined information portions of the data transfer format information.6. The data transmission method as set forth in claim 5, wherein and insaid dedicated protocol communicating, communication is conductedbetween said display device and said control unit via a dedicatedcommunication line.